The OPC Foundation started in 1994[1], as a task force comprised of five industrial automation vendors, with the purpose of creating a basic OLE for Process Control specification. OLE is a technology developed by Microsoft Corporation for the MS Windows operating system. The task force released the OPC standard in August 1996. The OPC Foundation was chartered to continue development of interoperability specifications and includes manufacturers and users of devices, instruments, controllers, software and enterprise systems.
This group of standards provides specifications for communicating real-time data from data acquisition devices such as PLC's to display and interface devices like Human-Machine Interfaces (HMI). The specifications focus on the continuous communication of data
OPC Alarm and Events
Standards for communicating alarm and event data on demand, as opposed to the continuous communications in the OPC Data Access group
This group of standards addresses server to server communications across industrial networks. The standards also address remote configuration, diagnostics, monitoring and management communications
An entirely new set of standards that incorporates all of the functionality of the above standards (and more), but does so using cross platform web services and other modern technology. OPC Unified Architecture